One of the greatest problems in the treatment of cancerous tumors is metastasis, i.e., the transmission of cells of a primary tumor to other locations in the patient and the establishment of new tumors at such locations. Metastasis is the primary cause of mortality in cancer; therefore the invasive capacity of cells is a major factor that determines the cancer treatment plan.
Moreover, metastasis is difficult to identify and control as metastasis often occurs before a primary tumor is detected and/or diagnosed; the point(s) of metastasis can increase to multiple sites with time and become highly difficult to treat by targeting a single location of metastasis, for example, using radiation or surgery on a specific tumor. Moreover, the metastatic lesions may be in locations which limit the possible dosages of the treatments, e.g., radiation, due to the sensitivity of the surrounding tissue to such treatments. Further, metastatic cells are heterogeneous, and cells which are resistant to conventional therapy tend to emerge.
Histological evidence of invasion usually mandates surgical and/or other aggressive treatments of the tumor. In prostate cancer and breast cancer, which has 217,730 and 207,090 new cases annually in the US, the decision to perform surgical procedures, such as prostatectomy (removal of prostate) and mastectomy (removal of the breast) must be made very carefully. Surgery, though potentially lifesaving, can lead to significant morbidity or mortality. The effect of serious physiological and psychological changes on a patient's life is often severe.
Tumor cell migration is strongly influenced by the mechanical and/or micro and nanostructural features of the extracellular matrix (ECM) in the tumor microenvironment (TME)1-3. These regulatory relationships are particularly important during metastatic dissemination toward distant sites where tumor cells must first successfully invade through the stroma and intravasate in order to metastasize8, 9, 10. As patient survival rate diminishes profoundly after a secondary tumor (or multiple tumors) has formed, understanding the key processes of the early metastatic cascade (e.g. invasion) is essential. During focal and local invasion, ECM environments with varying stiffness and orientation play critical roles in regulating the successive events necessary for cell migration9. Indeed, recent studies demonstrate that alignment of the collagen matrix containing both nanoscale cues from collagen fibrils and microscale cues from collagen fibers in the stroma of murine mammary and human breast carcinoma drive invasion through the stroma and predict poor outcome for human breast cancer patients6, 14, 15.
Measuring the invasion of cells isolated from tumors in an in vitro assay can yield results which are complimentary to histological examinations of tumor biopsies. The uses of existing invasion assays are limited as these typically require complex 3D imaging and time lapse microscopy. Additionally, other high-throughput invasion assays (e.g. TRANSWELL™) have limited capacity to position cells in a 3D environment. Controlled positioning of cells in 3D is possible using microfabricated hydrogels and microfluidics devices, however, these techniques require specialized infrastructure and expertise in microfabrication, and are expensive, require skilled personnel, and can only process a limited number of samples at once. Accordingly, there remains a need for a high-throughput, cost-effective method to efficiently and accurately identify cells with metastatic potential and/or invasiveness, as well screens to identify agents and compounds capable of inhibiting tumor cell migration and/or metastatic growth.